The present invention relates to the field of tumour treatment by administration of a prodrug that is converted into a drug at the site of the tumour. In particular, the invention relates to prodrugs which may be converted into a drug by the catalytic action of FAPxcex1, their manufacture and pharmaceutical use.
The human fibroblast activation protein (FAPxcex1) is a M, 95,000 cell surface molecule originally identified with monoclonal antibody (mAb) F19 (Rettig et al. (1988) Proc. Natl. Acad. Sci. USA 85, 3110-3114; Rettig et al. (1993) Cancer Res. 53, 3327-3335). The FAPxcex1 cDNA codes for a type II integral membrane protein with a large extracellular domain, trans-membrane segment, and short cytoplasmic tail (Scanlan et al. (1994) Proc. Natl. Acad. Sci. USA 91, 5657-5661; WO 97/34927). FAPxcex1 shows 48% amino acid sequence identity to the T-cell activation antigen CD26, also known as dipeptidyl peptidase IV (DPPIV; EC 3.4.14.5), a membrane-bound protein with dipeptidyl peptidase activity (Scanlan et al., loc. cit.). FAPxcex1 has enzymatic activity and is a member of the serine protease family, with serine 624 being critical for enzymatic function (WO 97/34927). Work using a membrane overlay assay revealed that FAPxcex1 dimers are able to cleave Ala-Pro-7-amino-4-trifluoromethyl coumarin, Gly-Pro-7-amino-4-trifluoromethyl coumarin, and Lys-Pro-7-amino-4-trifluoromethyl coumarin dipeptides (WO 97/34927).
FAPxcex1 is selectively expressed in reactive stromal fibroblasts of many histological types of human epithelial cancers, granulation tissue of healing wounds, and malignant cells of certain bone and soft tissue sarcomas. Normal adult tissues are generally devoid of detectable FAPxcex1, but some foetal mesenchymal tissues transiently express the molecule. In contrast, most of the common types of epithelial cancers, including  greater than 90% of breast, non-small-cell lung, and colorectal carcinomas, contain FAPxcex1-reactive stromal fibroblasts (Scanlan et al., loc. cit.). These FAPxcex1+ fibroblasts accompany newly formed tumour blood vessels, forming a distinct cellular compartment interposed between the tumour capillary endothelium and the basal aspect of malignant epithelial cell clusters (Welt et al. (1994) J. Clin. Oncol. 12(6), 1193-1203). While FAPxcex1+ stromal fibroblasts are found in both primary and metastatic carcinomas, the benign and premalignant epithelial lesions tested (Welt et al., loc. cit.), such as fibroadenomas of the breast and colorectal adenomas, only rarely contain FAPxcex1+ stromal cells. Based on the restricted distribution pattern of FAPxcex1 in normal tissues and its uniform expression in the supporting stroma of many malignant tumours, clinical trials with 131I-labeled mAb F19 have been initiated in patients with metastatic colon carcinomas (Welt et al., loc. cit.).
For new cancer therapies based on cytotoxic or cytostatic drugs, a major consideration is to increase the therapeutic index by improving the efficacy of cancerous tissue killing and/or reducing the toxicity for normal tissue of the cytotoxic or cytostatic agents. To increase specificity of tumour tissue killing and reduce toxicity in normal tissues, trigger mechanisms can be designed so that the toxic agents synthesised in their prodrug or inactive forms are rendered active when and where required, notably in the cancerous tissues (Panchal (1998) Biochem. Pharmacol. 55, 247-252). Triggering mechanisms may include either exogenous factors such as light or chemicals or endogenous cellular factors, such as enzymes with restricted expression in cancer tissues. Another concept, that has been further elaborated, is called xe2x80x98antibody-directed enzyme prodrug therapyxe2x80x99 (ADEPT) or xe2x80x98antibody-directed catalysisxe2x80x99 (ADC) (Huennekens (1994) Trends Biotechnol. 12, 234-239; Bagshawe (1994) Clin. Pharmacokinet. 27, 368-376; Wang et al. (1992) Cancer Res. 52, 4484-4491; Sperker et al. (1997) Clin. Pharmacokinet. 33(1), 18-31). In ADEPT, an antibody directed at a tumour-associated antigen is used to target a specific enzyme to the tumour site. The tumour-located enzyme converts a subsequently administered prodrug into an active cytotoxic agent. The antibody-enzyme conjugate (AEC) binds to a target antigen on cell membranes or to free antigen in extracellular fluid (ECF). A time interval between giving the AEC and prodrug allows for the AEC to be cleared from normal tissues so that the prodrug is not activated in the normal tissues or blood. However, some disadvantages of ADEPT are related to the properties of the AEC (Bagshawe, loc. cit.). For example, in humans, only a small fraction of the administered dose of the targeting ACE binds to tumour tissue and the remainder is distributed through body fluids from which it is cleared with significant time delays. Even very low concentrations of targeted enzyme can catalyse enough prodrug to have toxic effects because plasma and normal ECF volumes are much greater than those of tumour ECF. The AEC may also be immunogenic, thus preventing repeat administration, in many instances.
The International patent applications WO 97/12624 and WO 97/14416 disclose oligopeptides including the following penta- and hexapeptide (SEQ.ID.NOs.: 151 and 177: hArg-Tyr-Gln-Ser-Ser-Pro; hArg-Tyr-Gln-Ser-Pro;), comprising amino acid sequences, which are recognized and proteolytically cleaved by free prostate specific antigen (PSA) and therapeutic agents which comprise conjugates of such oligopeptides and known therapeutic or cytotoxic agents. These oligopeptide conjugates which comprise at least one glutamineserine moiety are useful for treatment of prostate cancer only.
The problem underlying the present invention was to provide methods and means for improving normal tissue tolerability of cytotoxic or cytostatic agents with known efficacy against a broad range of tumour tissues.
The present invention relates to enzyme-activated anti-tumour compounds. In particular, the invention provides prodrugs that are capable of being converted into drugs by the catalytic action of endogenous fibroblast activating protein alpha (FAPxcex1) shown to reside in human cancer tissues. Preferably, a prodrug of the present invention is capable of being converted into a drug by the catalytic action of FAPxcex1, said prodrug having a cleavage site which is recognised by FAPxcex1, and said drug being cytotoxic or cytostatic against cancer cells under physiological conditions.
In the context of this invention, a xe2x80x9cdrugxe2x80x9d shall mean a chemical compound that may be administered to humans or animals as an aid in the treatment of disease. In particular, a drug is an active pharmacological agent.
The term xe2x80x9ccytotoxic compoundxe2x80x9d shall mean a chemical compound which is toxic to living cells, in particular a drug that destroys or kills cells. The term xe2x80x9ccytostatic compoundxe2x80x9d shall mean a compound that suppresses cell growth and multiplication and thus inhibits the proliferation of cells. Examples for cytotoxic or cytostatic compounds suitable for the present invention are anthracycline derivatives such as doxorubicin, analogs of methotrexate such as methothrexate, pritrexime, trimetrexate or DDMP, melphalan, analogs of cisplatin such as cisplatin, JM216, JM335, bis(platinum) or carboplatin, analogs of purines and pyrimidines such as cytarbine, gemcitabine, azacitidine, 6-thioguanine, flurdarabine or 2-deoxycoformycin, and analogs of other chemotherapeutic agents such as 9-aminocamptothecin, D,L-aminoglutethimide, trimethoprim, pyrimethamine, mitomycin C, mitoxantrone, cyclophosphanamide, 5-fluorouracil, extramustine, podophyllotoxin, bleomycin or taxol.
A xe2x80x9cprodrugxe2x80x9d shall mean a compound that, on administration, must undergo chemical conversion by metabolic processes before becoming an active pharmacological agent. In particular, a prodrug is a precursor of a drug. In the context of the present invention, the prodrug is significantly less cytotoxic or cytostatic than the drug it is converted into upon the catalytic action of FAPxcex1. The expert knows methods of determining cytotoxicity of a compound, see e.g. example 6 herein, or Mosmann ((1983) J. Immun. Meth. 65, 55-63). Preferably, the prodrug is at least three times less cytotoxic as compared to the drug in an in vitro assay.
A xe2x80x9cdrug being cytostatic or cytotoxic under physiological conditionsxe2x80x9d shall mean a chemical compound which is cytostatic or cytotoxic in a living human or animal body, in particular a compound that kills cells or inhibits proliferation of cells within a living human or animal body.
A xe2x80x9cprodrug having a cleavage site which is recognised by FAPxcex1xe2x80x9d shall mean a prodrug which can act as a substrate for the enzymatic activity of FAPxcex1. In particular, the enzymatic activity of FAPxcex1 can catalyse cleavage of a covalent bond of the prodrug under physiological conditions. By cleavage of this covalent bond, the prodrug is converted into the drug, either directly or indirectly. Indirect activation would be the case if the cleavage product of the FAPxcex1 catalysed step is not the pharmacologically active agent itself but undergoes a further reaction step, e.g. hydrolysis, to become active. More preferably, the cleavage site of the prodrug is specifically recognised by FAPxcex1, but not by other proteolytic enzymes present in the human or animal body. Also preferably, the cleavage site is specifically recognised by FAPxcex1, but not by proteolytic enzymes present in human or animal body fluids, especially plasma. In a particularly preferred embodiment, the prodrug is stable in plasma, other body fluids, or tissues, in which biologically active FAPxcex1 is not present or detectable. Preferably, in an in vitro assay as carried out in Example 7 herein, more than 50%, more preferably more than 80%, more preferably more than 90% of the prodrug are still present in a solution containing 10% (v/v) of human plasma after 8 h at 37xc2x0 C. The cleavage site should most preferably be specific for FAPxcex1. In a preferred embodiment, the cleavage site comprises a L-proline residue which is linked to a cytotoxic or cytostatic drug via an amide bond. An example of this class is a doxorubicin-peptide conjugate. FAPxcex1 may catalyse the cleavage of a peptidic bond between the C-terminal amino acid residue of the peptide, which is preferably L-proline, and the cytotoxic or cytostatic compound.
Preferred compounds show at least 10% conversion to free drug, under standard conditions listed below. More preferred are compounds that show at least 20% conversion to free drug, under standard conditions. Even more preferred are compounds that show at least 50% conversion to free drug, under standard conditions. In this context, standard conditions are defined as follows: Each compound is dissolved in 50 mM Hepes buffer, 150 mM NaCl, pH 7.2, at a final concentration of 5 xcexcM and incubated with 100 ng CD8FAPxcex1 (see example 4) for 24 hours at 37xc2x0 C. Release of free drug by CD8FAPxcex1 is determined as described in example 5.
Preferably, the present invention relates to a compound of formula (I) 
or a pharmaceutically acceptable salt thereof, wherein
R1 represents an amino alkanoyl, an oligopeptidoyl, in particular a di- or tripeptidoyl group, the N-terminal amino function of which may be attached to a capping group;
R1 and Rb together with the interjacent Nxe2x80x94C group form an optionally substituted, optionally benzo- or cyclohexano-condensed 3- to 7-membered saturated or unsaturated heterocyclic ring, in which one or two CH2 groups may also be replaced by NH, O or S,
R4 represents H, C1-C6-alkyl, C3-C8-cycloalkyl, aryl or heteroaryl; and
Cytxe2x80x2 represents the residue of a cytotoxic or cytostatic compound,
with the proviso that,
N2-acetyl-L-homoarginyl-L-tyrosyl-L-glutaminyl-L-seryl-N-[2,3,6-trideoxy-1-O-[(1S,3S)-1,2,3,4,6,11-hexahydro-3,5,12-trihydroxy-3-(hydroxyacetyl)-10-methoxy-6,11-dioxo-1-naphthacenyl]-.alpha.-L-lyxo-hexopyranos-3-yl]-L-prolinamide; and
N2-acetyl-L-homoarginyl-L-tyrosyl-L-glutaminyl-L-seryl-L-seryl-N-[2,3,6-trideoxy-1-O-[(1S,3S)-1,2,3,4,6,11-hexahydro-3,5,12-trihydroxy-3-(hydroxyacetyl)-10-methoxy-6,11-dioxo-1-naphthacenyl]-.alpha.-L-lyxo-hexopyranos-3-yl]-L-prolinamide are excluded.
Particularly preferred are those compounds of formula I, wherein R1 is a residue of formula
Cgxe2x80x94A, Cgxe2x80x94Bxe2x80x94A or Cgxe2x80x94(D)mxe2x80x94Bxe2x80x94A, in which
Cg represents a hydrogen atom, or a capping group selected from the group consisting of R5xe2x80x94CO, R5xe2x80x94Oxe2x80x94COxe2x80x94, R5xe2x80x94NHxe2x80x94COxe2x80x94, R5xe2x80x94SO2xe2x80x94 or R5xe2x80x94, wherein R5 is an optionally substituted C1-C6-alkyl, C3-C8-cycloalkyl, aryl, aralkyl or heteroaryl group;
preferably Cg is an acetyl, benzoyl, D-alanyl, (R)xe2x80x94H2NCH(CH3)xe2x80x94, or H2NCOCH2CH2xe2x80x94 substituent or another capping group for the protection of the N-terminal amino function;
A, B and D each independently represent moieties derived from amino carboxylic acids of the formula xe2x80x94[NR6xe2x80x94(X)pxe2x80x94CO]xe2x80x94 wherein X represents CR7R8 and wherein R6, R7 and R8 each independently represent a hydrogen atom, an optionally substituted C1-C6-alkyl, C3-C8-cycloalkyl, aryl or heteroarylgroup, and p is 1, 2, 3, 4, 5; or
A, B and D each independently represent moieties derived from cyclic amino carboxylic acids of formula 
xe2x80x83wherein
R9 represents C1-C6-alkyl, OH, or NH2,
m is an integer from 1 to 10,
q is 0, 1 or 2; and
r is 0, 1 or 2.
Furthermore preferred are those compounds of formula I, wherein R6, R7 and R8 each independently represent a hydrogen atom or CH3xe2x80x94, CH3CH2xe2x80x94, CH3CH2CH2xe2x80x94, (CH3)2CHxe2x80x94, CH3CH2CH2CH2xe2x80x94, (CH3)2CHCH2xe2x80x94, CH3CH2CH(CH3)xe2x80x94, (CH3)3Cxe2x80x94, HOCH2xe2x80x94, CH3CH(OH)xe2x80x94, CH3CH(OH)CH2CH2xe2x80x94, HOCH2CH2CH2CH2xe2x80x94, H2NCH2CH2CH2xe2x80x94, H2NCH2CH2CH2CH2xe2x80x94, H2NCH2CH(OH)CH2CH2xe2x80x94, H2NC(xe2x95x90NH)NHCH2CH2CH2xe2x80x94, HSCH2xe2x80x94, CH3SCH2CH2xe2x80x94, HOOCCH2xe2x80x94, HOOCCH2CH2xe2x80x94, H2NC(xe2x95x90O)CH2xe2x80x94, H2NC(xe2x95x90O)CH2CH2xe2x80x94, benzyl, para-hydroxy-benzyl, 
cyclohexyl, phenyl, p is 1, and wherein the configuration at CR7R8 can be R or S; if R7 is other than H, then R8 is preferably H; R6 is preferably H; if p is greater than one, R7 and R8 are preferably H;
Another preferred embodiment of the present invention are those compounds of formula I, wherein the heterocyclic ring formed by Ra, Rb and the interjacent Nxe2x80x94C is substituted by R2 and R3, wherein R2 and R3 each independently represent a hydrogen or halogen atom or a C1-C6-alkyl, C1-C6-alkylamino, di-C1-C6-alkylamino, C1-C6-alkoxy, thiol, C1-C6-alkylthio, oxo, imino, fomyl, C1-C6-alkoxy carbonyl, amino carbonyl, C3-C8-cycloalkyl, aryl, or heteroaryl group.
Unless indicated otherwise, the simple stereoisomers as well as mixtures or racemates of the stereoisomers are included in the invention.
xe2x80x9cC1-C6-alkylxe2x80x9d generally represents a straight-chained or branched hydrocarbon radical having 1 to 6 carbon atoms.
The term xe2x80x9coptionally substitutedxe2x80x9d as used hereinabove or hereinbelow with respect to a group or a moiety refers to a group or moiety which may optionally be substituted by one or several halogen atoms, hydroxyl, amino, C1-C6-alkyl-amino, di- C1-C6-alkyl-amino, C1-C6-alkyl-oxy, thiol, C1-C6-alkyl-thio, xe2x95x90O, xe2x95x90NH, xe2x80x94CHO, xe2x80x94COOH, xe2x80x94CONH2, xe2x80x94NHC(xe2x95x90NH)NH2, C3-C8-cycloalkyl, aryl, or heteroaryl substituents, which may be identical to one another or different.
The following radicals may be mentioned by way of example:
Methyl, ethyl, propyl, 1-methylethyl (isopropyl), butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethyl-propyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl and 1-ethyl-2methyl-propyl, HOCH2xe2x80x94, CH3CH(OH)xe2x80x94, CH3CH(OH)CH2CH2xe2x80x94, HOCH2CH2CH2CH2xe2x80x94, H2NCH2CH2CH2xe2x80x94, H2NCH2CH2CH2CH2xe2x80x94, H2NCH2CH(OH)CH2CH2xe2x80x94, H2NC(xe2x95x90NH)NHCH2CH2CH2xe2x80x94, HSCH2xe2x80x94, CH3SCH2CH2xe2x80x94, HOOCCH2xe2x80x94, HOOCCH2CH2xe2x80x94, H2NC(xe2x95x90O)CH2xe2x80x94, H2NC(xe2x95x90O)CH2CH2xe2x80x94, benzyl, para-hydroxy-benzyl, 
If a C1-C6-alkyl group is substituted, the substituents are preferably hydroxyl, amino, dimethylamino, diethylamino, thiol, methyl-thiol, methoxy, ethoxy, xe2x95x90O, xe2x95x90NH, xe2x80x94CHO, xe2x80x94COOH, xe2x80x94COOCH3, xe2x80x94COOCH2CH3, xe2x80x94CONH2, xe2x80x94NHC(xe2x95x90NH)NH2, cyclohexyl, phenyl, benzyl, para-hydroxy-benzyl, 
If C1-C6-alkyl is substituted with aryl or heteroaryl, C1-C6-alkyl is preferably C1, more preferably a methylene group.
The terms xe2x80x9camino alkanoylxe2x80x9d and xe2x80x9coligopeptidoylxe2x80x9d including xe2x80x9cdi- or tripeptidoylxe2x80x9d as used hereinabove or hereinbelow with respect to radical R1 describe a radical in which an amino acid or an oligomer comprising up to 12, preferably 2 or 3 amino acid moieties is attached C-terminally to the nitrogen atom of the heterocyclic ring via an amid bond.
A person of ordinary skill in the chemistry of amino acids and oligopeptides will readily appreciate that certain amino acids may be replaced by other homologous, isosteric and/or isolectronic amino acids wherein the biological activity of the original amino acid or oligopeptide has been conserved upon modification. Certain unnatural and modified natural amino acids may also be utilized to replace the corresponding natural amino acid. Thus, for example, tyrosine may be replaced by 3-iodotyrosine, 2- or 3-methyltyrosine, 3-fluorotyrosine.
The term xe2x80x9ccapping groupxe2x80x9d as used hereinabove or hereinbelow with respect to a group which is attached to the N-terminal nitrogen atom of the amino alkanoyl or oligopeptidoyl group of radical R1 defines a group or moiety which reduces or eliminates the enzymatic degradation of the compounds of the present invention by the action of amino peptidases which are present in the blood plasma of warm blooded animals. Suitable capping groups include C1-C10 alkanoyl, C6-C18-aryl-C1-C10-alkanoyl, C6-C18-aryl-C1-C10-alkylsulfonyl. Such capping groups also include hydrophilic blocking groups, which are chosen upon the presence of hydrophilic functionality. Such capping groups increase the hydrophilicity of the compounds of the present invention and thus enhance their solubility in aqueous media. These hydrophilicity enhancing capping groups are preferably selected from hydroxylated alkanol, polyhydroxylated alkanoyl, hydroxylated aroyl, hydroxylated arylalkanoyl, polyhydroxylated aroyl, polyhydroxylated arylalkanoyl, polyethylene glycol, glycosylates, sugars, and crown ethers.
xe2x80x9cC3-C8-Cycloalkylxe2x80x9d generally represents cyclic hydrocarbon radical having 3 to 8 carbon atoms which may optionally be substituted by one or several hydroxyl, amino, C1-C6-alkyl-amino, di-C1-C6-alkyl-amino, C1-C6-alkyl, C1-C6-alkyloxy, thiol, C1-C6-alkyl-thio, xe2x95x90O, xe2x95x90NH, xe2x80x94CHO, xe2x80x94COOH, xe2x80x94COOCH3, xe2x80x94COOCH2CH3, xe2x80x94CONH2, xe2x80x94NHC(xe2x95x90NH)NH2, or halogen substituents , which may be identical to one another or different.
xe2x80x9cHeterocyclic ringxe2x80x9d as used hereinabove and hereinbelow with respect to the group formed by Ra and Rb together with the interjacent Nxe2x80x94C group generally represents a 3 to 7-membered, preferably 4-, 5- or 6-membered non-aromatic heterocyclic ring system, containing one nitrogen atom and optionally 1 or 2 additional heteroatoms selected from the group of nitrogen, oxygen and sulfur, which may be substituted by one or several halogen atoms or C1-C6-alkyl, C1-C6-alkylamino, di-C1-C6-alkylamino, C1-C6-alkoxy, thiol, C1-C6-alkylthio, oxo, imino, fomyl, C1-C6-alkoxy carbonyl, amino carbonyl, C3-C8-cycloalkyl, aryl, or heteroaryl groups, which may be identical to one another or different, and which optionally may be benzo- or cyclohexano-condensed. Such heterocyclic rings are preferably azetidine or are derived from a fully or partially hydrogenated pyrrole, pyridine, thiazole, isoxazole, pyrazole, imidazole, indole, benzimidazole, indazole, pyridazine, pyrimidine, pyrazin group. Most preferred are azetidine, pyrrolidine, 3,4-dehydropyrrolidine, piperidine, hexahydro-1H-azepine, octahydroindole, imidazolidine, thiazolidine.
If such heterocyclic ring is substituted, the substituents are preferably methyl, ethyl, propyl, 1-methylethyl (isopropyl), butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, droxyl, amino, dimethyl-amino, diethyl-amino, thiol, methyl-thiol, methoxy, ethoxy, xe2x80x94CHO, xe2x80x94COOH, xe2x80x94COOCH3, xe2x80x94COOCH2CH3, or xe2x80x94CONH2.
xe2x80x9cArylxe2x80x9d generally represents an aromatic ring system with 6 to 10, preferably 6 carbon atoms which may optionally be substituted by one or several hydroxyl, amino, C1-C6-alkyl-amino, di-C1-C6-alkyl-amino, C1-C6-alkyl, C1-C6-alkyloxy, thiol, C1-C6-alkyl-thio, xe2x80x94CHO, xe2x80x94OOH, xe2x80x94COOCH3, xe2x80x94COOCH2CH3, xe2x80x94CONH2, or halogen substituents, which may be idential to one another or different, and which optionally may be benzocondensed. Aryl subtituents may be preferably derived form benzene, preferred examples being phenyl, 2-hyroxy-phenyl, 3-hydroxy-phenyl, 4-hydroxy-phenyl, 4-amino-phenyl, 2-amino-phenyl, 3-amino-phenyl.
If aryl is substituted, the substituents are preferably methyl, ethyl, propyl, 1-methylethyl (isopropyl), butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, hydroxyl, amino, dimethyl-amino, diethyl-amino, thiol, methyl-thiol, methoxy, ethoxy, xe2x80x94CHO, xe2x80x94COOH, xe2x80x94COOCH3, xe2x80x94COOCH2CH3, or xe2x80x94CONH2.
xe2x80x9cHeteroarylxe2x80x9d generally represents a 5 to 10-membered aromatic heterocyclic ring system, containing 1 to 5 heteroatoms selected from the group of nitrogen, oxygen, or sulfur, which may optionally be substituted by one or several hydroxyl, amino, C1-C6-alkyl-amino, di-C1-C6-alkyl-amino, C1-C6-alkyl, C1-C6-alkyloxy, thiol, C1-C6-alkyl-thio, xe2x80x94CHO, xe2x80x94COOH, COOCH3, xe2x80x94COOCH2CH3, xe2x80x94CONH2, or halogen substituents, which may be identical to one another or different, and which optionally may be benzocondensed. Heteroaryl substituents may preferably be derived from furane, pyrrole, thiophene, pyridine, thiazole, isoxazole, pyrazole, imidazole, benzofuran, thianaphthene, indole, benzimidazole, indazole, chinoline, pyridazine, pyrimidine, pyrazin, chinazoline, pyrane, purine, adenine, guanine, thymine, cytosine, uracil.
If heteroaryl is substituted, the substituents are preferably methyl, ethyl, propyl, 1-methylethyl (isopropyl), butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, hydroxyl, amino, dimethyl-amino, diethyl-amino, thiol, methyl-thiol, methoxy, ethoxy, xe2x80x94CHO, xe2x80x94COOH, xe2x80x94COOCH3, xe2x80x94COOCH2CH3, or xe2x80x94CONH2.
xe2x80x9cResidue of a cytotoxic or cytostatic compoundxe2x80x9d means that the compound H2Nxe2x80x94Cytxe2x80x2, which is released upon cleavage of the amide bond shown in formula (I), is either cytotoxic or cytostatic itself, or may be converted into a cytotoxic or cytostatic compound in a subsequent step.
In the latter case, xe2x80x94Cytxe2x80x2 may be a residue of formula xe2x80x94Lxe2x80x94Cytxe2x80x3, wherein L is a linker residue derived from a bifunctional molecule, for instance a diamine H2Nxe2x80x94Lxe2x80x2xe2x80x94NH2, an amino alcohol H2Nxe2x80x94Lxe2x80x2xe2x80x94OH, for example p-amino-benzyl alcohol (PABOH), an amino carbonate, for example 
or an unnatural amino carboxylic acid. If xe2x80x94Cytxe2x80x2 is of formula xe2x80x94Lxe2x80x94Cytxe2x80x3, the compound H2Nxe2x80x94Lxe2x80x2xe2x80x94Cytxe2x80x3 is generated by the enzymatic cleavage of the amide bond shown in formula (I). The compound H2Nxe2x80x94Lxe2x80x2xe2x80x94Cytxe2x80x3 may be cytotoxic or cytostatic itself or the linker residue cleaved off from Cytxe2x80x3 in a subsequent step releasing the cytotoxic or cytostatic agent. For example, the compound H2Nxe2x80x94Lxe2x80x2xe2x80x94Cytxe2x80x3 may be hydrolysed under physiological conditions into a compound H2Nxe2x80x94Lxe2x80x2xe2x80x94OH and the cytotoxic or cytostatic compound Hxe2x80x94Cytxe2x80x3, which is the active therapeutic agent (In the following, only the term Cytxe2x80x2 is used for both Cytxe2x80x2 and Cytxe2x80x3, and only the term L is used for both L and Lxe2x80x2, for simplicity).
The pharmaceutically acceptable salts of the compounds of the present invention include the conventional non-toxic salts formed from non-toxic inorganic or organic acids. For example, such conventional non-toxic salts include those from inorganic acids such as hydrochloric acid, hydrobromic, sulfuric, sulfamic, phosphoric, nitric and the like; and the salts prepared from organic acids such as acetic, propionic, succinic, glycolic, stearic, lactic, malic, tartaric, citric, ascorbic, maleic, phenylacetic, glutamic, benzoic, salicylic, sulfanilic, oxalictrifluoroacetic and the like.
Preferred compounds of formula I are those of fomula IA 
wherein R2, R3, R4, Cytxe2x80x2 are as defined hereinabove,
R1 represents an amino alkanoyl or oligopeptidoyl group, and
Xxe2x80x94Y represents CHR2xe2x80x94CH2, CR2xe2x95x90CH, NHxe2x80x94CH2, CH2xe2x80x94NH, xe2x80x94CR2xe2x80x94, CH2xe2x80x94CHR2xe2x80x94CH2; with the proviso that R1 represents an amino alkanoyl, di- or tripeptidoyl group or R1 represents an oligopeptidoyl having more than three amino acid moieties which does not contain a Gln-Ser amino acid sequence, in the event that Xxe2x80x94Y represents a CH2xe2x80x94CH2 group.
Preferably the xcex1 carbon atom of the cyclic amino acid residue is racemic, i.e. of (R/S) configuration, most preferably of (S) configuration; in a particularly prefererred embodiment, the xcex1 carbon atom is of (S) configuration and R2 is H. In the event that R2 is OH, it is preferably in trans position.
R2, R3 preferably represent a hydrogen atom or a methyl, ethyl, propyl, isopropyl, phenyl, methoxy, ethoxy or hydroxy group, most preferably a hydrogen atom. R4 is preferably a hydrogen atom or a methyl, ethyl, propyl, isopropyl or phenyl group, most preferably a hydrogen atom.
Particularly preferred compounds of formula IA are selected from the formulae IA1, IA2, IA3, IA4 and IA5
H2Nxe2x80x94Cytxe2x80x2 is preferably an anthracycline derivative of formula II 
wherein
Rc represents C1-C6 alkyl, C1-C6 hydroxyalkyl or C1-C6 alkanoyloxy C1-C6 alkyl, in particular methyl, hydroxymethyl, diethoxyacetoxymethyl or buryryloxymethyl;
Rd represents hydrogen, hydroxy or C1-C6 alkoxy, in particular methoxy;
one of Re and Rf represents a hydrogen atom; and the other represents a hydrogen atom or a hydroxy or tetrahydropyrany-2-yloxy (OTHP) group.
Paricularly preferred are the following compounds of formula II:
Most preferred is doxorubicin (Dox). Other cytotoxic or cytostatic residues Cytxe2x80x2 may be derived for example from methotrexate, trimetrexate, pyritrexim, 5,10-dideazatetrahydrofolatepyrimetamine, trimethoprim, 10-propargyl-5,8-dideazafolate-2,4-diamino-5(3xe2x80x2,4xe2x80x2-dichloropheyl)-6-methylpyrimidine, aminoglutethimide, goreserelin, melphalan, chlorambucil, analogs of other chemotherapeutic agents such as 9-aminocamtothecin (for examples see e.g. Burris HA, r. d. and S. M. Fields (1994). xe2x80x9cTopoisomerase I inhibitors. An overview of the camptothecin analogs. [Review].xe2x80x9d Hematol. Oncol. Clin. North Am. 8(2): 333-355; Iyer, L. and M. J. Ratain (1998). xe2x80x9cClinical pharmacology of camptothecins. [Review] [137 refs].xe2x80x9d Cancer Chemother. Pharmacol. 42 Suppl: S31-S43.)
In formula (I), Cytxe2x80x2 may also be a biological effector molecule which either directly or indirectly effects destruction of tumour cells, like for example TNFxcex1.
Preferred examples of amino carboxylic acids from which the A, B, and D units may be derived are glycine (Gly), or the D- or, more preferably, the L-forms of alanine (Ala), valine (Val), leucine (Leu), isoleucine (lle), phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp), cysteine (Cys), methionine (Met), serine (Ser), threonine (Thr), lysine (Lys), arginine (Arg), histidine (His), aspartatic acid (Asp), glutamic acid (Glu), asparagine (Asn), glutamine (Gln), proline (Pro), trans-4-hydroxy-proline (Hyp), 5-hydroxy-lysine (Hyl), norleucine (Nle), 5-hydroxynorleucine, 6-hydroxynorleucine (Hyn), omithine (Orn), cyclohexylglycine (Chg), phenylglycine (Phg), glutamine (Gln), cyclohexylalanine (Cha), methionine-S-oxide (Met), xcex2-cyclopropylalanine (Cpa), tert.-leucine (Tle), or homo-serine (Hse).
Preferred compounds have the general formula (I), wherein the A unit is derived from alanine, valine (Val), leucine (Leu), isoleucine (Ile), phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp), cysteine (Cys), methionine (Met), serine (Ser), threonine (Thr), lysine (Lys), arginine (Arg), histidine (His), aspartatic acid (Asp), glutamic acid (Glu), asparagine (Asn), glutamine (Gln), proline (Pro), trans-4-hydroxy-proline (Hyp), 5-hydroxy-lysine (Hyl), norleucine (Nle), 5-hydroxynorleucine, 6-hydroxynorleucine (Hyn), ornithine (Orn), or cyclohexylglycine (Chg), phenylglycine (Phg), glutamine (Gln), cyclohexylalanine (Cha), methionine-S-oxide (Met), xcex2-cyclopropylalanine (Cpa), tert.-leucine (Tle) or homoserine (Hse).
Particularly preferred are those compounds of formula (I), wherein R1 is a group selected from the formnulae (1) to (34):
wherein
Cg represents a hydrogen atom or a capping group selected from benzoyloxycarbonyl, phenylacetyl, phenylmethylsulfonyl and benzylaminocarbonyl; Xaa represents a moiety derived from an amino carboxylic acid, preferably selected form the group natural amino acids, in particular from the group consisting of Ala, Pro, Tyr, Phe, His, Ser, Thr, Hyp and Lys; and m is an integer from 1 to 6.
Preferred capping groups Cg are acetyl (Ac), succinimidyl (Suc), D-alanyl, benzyloxycarbonyl (Cbz or Z), or macromolecules such as polyethylene glycol.
Preferred anthracycline prodrugs are the compounds of formula III 
wherein Ra, Rb, Rc, Rd, Re, Rf and R1 are as defined hereinabove.
Most preferred compounds of the invention are doxorubicin derivatives of formulae (IIIA) to (IIIF): 
If the part Cgxe2x80x94Bxe2x80x94A or Cgxe2x80x94(D)m_Bxe2x80x94A of formula (I) contains two or more sulfur atoms, the compound of the invention may contain one or more disulfide bonds.
One class of cytotoxic or cytostatic compounds which may be used for the present invention has a primary amino function which is available for formation of an amidic bond as shown in formula (I), like doxorubicin. In this case, a linker molecule L is not necessary. If a cytostatic or cytotoxic compound does not have such an amino function, such a function may be created in such a compound by way of chemical modification, e.g. by introducing or converting a functional group or attaching a linker molecule to the compound. A linker molecule may also be inserted between the oligomeric part (i.e. the part comprising the amino carboxylic residues) and the cytostatic or cytotoxic part of the compound of the invention to ensure or optimise cleavage of the amide bond between the oligomeric part and the cytotoxic or cytostatic part. If a linker molecule is present, i.e. in compounds containing the structure Lxe2x80x94Cytxe2x80x2, the bond between L and Cytxe2x80x2 is preferably an amidic or ester bond. In a preferred embodiment, such a linker molecule is hydrolysed off the cytostatic or cytotoxic compound under physiological conditions after the enzymatic cleavage and thus the free cytostatic or cytotoxic compound is generated. In any case, the compound of the invention must have the property of being cleavable upon the catalytic action of FAPxcex1 and, as a direct or indirect consequence of this cleavage, releasing under physiological conditions a cytostatic or cytotoxic compound.
In a further aspect, the present invention relates to a prodrug that is capable of being converted into a drug by the catalytic action of FAPxcex1, said prodrug having a cleavage site which is recognised by FAPxcex1, and said drug being cytotoxic or cytostatic under physiological conditions. Such a prodrug preferably comprises an oligomeric part comprising two or more amino carboxylic residues and a cytotoxic or cytostatic part, wherein the C-terminal amino carboxylic residue of the oligomeric part is a 3- to 7-membered natural or unnatural cyclic amino acid, preferably D- or L-proline, or D- or L-hydroxyproline, and the C-terminal carboxy function is linked to the cytotoxic or cytostatic part by an amide bond which may be cleaved by the catalytic action of FAPxcex1. The oligomeric part is preferably a peptide. Preferably, the oligomeric part comprises two, three, four, five, six, seven, eight, nine, ten, eleven, or twelve amino carboxylic acid residues, more preferably two, three, or four amino carboxylic residues. The N-terminal amino function is preferably protected by a capping group.
The compounds of the invention may be synthesized by processes known in the art (E. Wxc3xcnsch, Synthese von Peptiden, in xe2x80x9cMethoden der organischen Chemiexe2x80x9d, Houben-Weyl (Eds. E. Mxc3xcller, O. Bayer), Vol. XV, Part 1 and 2, Georg Thieme Verlag, Stuttgart, 1974). For example, the compounds could be synthesized in a block synthetic fashion by condensation of the terminal carboxy function of the oligomeric part, wherein X may be OH or an activation leaving group, with the amino group of the cytotoxic or cytostatic molecule H2Nxe2x80x94Cytxe2x80x2 resulting in an amide formation. 
If a linker residue (L) is required between the oligomeric part and the cytotoxic or cytostatic agent the block synthesis can be done in the same manner. 
If the cytotoxic or cytostatic bears a carboxy function for the attachment to the oligomeric part, the linker molecule can be an imine or an amino alcohol and the block synthesis of such compounds can be carried out in a similar way by reaction of the activated XOCxe2x80x94Cytxe2x80x2 with either the hydroxy or the amino component. 
If the cytotoxic or cytostatic reagent has a hydroxy function which is suitable for the coupling to the oligomeric part the linker residue may be an amino carboxylic acid and a block synthesis can be done similarly.
If necessary, other functional groups in the units Cytxe2x80x2, L, hydroxyproline, A, B and D which shall not react during the assembly of the target molecules may be protected by suitable protecting groups. Suitable protecting groups are well known from the state of the art (P. G. M. Wuts, xe2x80x9cProtective groups in organic synthesisxe2x80x9d, John Wiley and Sons Inc., New York 1991). These protecting groups are removed at the end of the synthesis.
By way of example only, useful amino-protecting groups may include, for example, C1-C10 alkanoyl groups such as formyl, acetyl dichloroacetyl, propionyl, 3,3diethylhexanoyl, and the like, C1-C10 alkoxycarbonyl and C6-C17 aralkyloxycarbonyl groups such as tert-butoxycarbonyl, benzyloxycarbonyl (BOC), fluorenylmethoxycarbonyl, and the like. Most preferred is fluorenylmethoxycarbonyl (FMOC).
Suitable carboxy-protecting groups may include, for example, C1-C10 alkyl groups such as methyl, tert-butyl, decyl; C6-C17 aralkyl such as benzyl, 4-methoxybenzyl, diphenylmethyl, triphenylmethyl, fluorenyl; tri-(C1-C10 alkyl)silyl or (C1-C10 alkyl)-diarylsilyl such as trimethylsilyl, dimethyl-tert-butylsilyl, diphenyl-tert-butylsilyl and related groups.
To achieve such ester- or amide formations, it may be necessary to activate the carbonyl group of the Larboxylic acid for a nucleophilic attack of an amine or alcohol, i.e. X to be an activation group or leaving group which is suitable to be substituted by an amino group. This activation can be done by conversion of the carboxylic acid into an acid chloride or acid fluoride or by conversion of the carboxylic acid into an activated ester, for instance a N-hydroxysuccinimidyl ester or a pentafluorophenyl ester. Another method of activation is the transformation into a symmetrical or unsymmetrical anhydride. Alternatively, the formation of the amide- or ester bonds can be achieved by the use of in situ coupling reagents like benzotriazole-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBOP) (E. Frerot et al., Tetrahedron, 1991, 47, 259-70), 1,1xe2x80x2-carbonyldimidazole (CDI) (K. Akaji et al., THL, 35, 1994, 3315-18), 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU) (R. Knorr et al., THL, 30, 1989, 1927-30), 1-(mesitylene-2-sulonyl)-3-nitro-1H-1,2,4-triazole (MSNT) (B. Blankenmeyer-Menge et al., THL, 31, 1990, 1701-04).
As an alternative to the block synthesis the molecules in the general formula (I) can be assembled in a step by step manner starting at the right hand side by stepwise condensation reactions of the respective monomers Cytxe2x80x2, L, the cyclic amino acid group formed by Ra, Rb and the inteijacent Nxe2x80x94C group, in particular proline or hydroxyproline, A, B and D. For the condensation reaction the same above mentioned coupling methods can be applied. to Since the units L, proline/hydroxyproline, A, B and D are at least bifunctional molecules containing an amino- and (at least the units A, B, D, and the cyclic amino acid group formed by Ra, Rb and the interhjacent Nxe2x80x94C group, in particular proline/hydroxyproline) a carboxy group, the amino group needs to be blocked by a protecting group (PG) prior to the activation of the carboxylic function. For the protection of the amino groups the group BOC or preferably the group FMOC can be applied. After the coupling reaction the amino protecting group has to be removed and the coupling with the next Fmoc- or Boc-protected unit can be carried out. If necessary, other functional groups in the units Cytxe2x80x2, L, the cyclic amino acid group formed by Ra, Rb and the interhjacent Nxe2x80x94C group, in particular hydroxyproline, A, B and D which shall not react during the assembly of the target molecules may be protected by suitable protecting groups. These protecting groups are removed at the end of the synthesis.
Capping groups as defined in the context of formula (I) may also serve as protection groups, in particular when the last (N-terminal) amino carboxylic acid unit is added. In this latter case the protecting group is not removed as it is a part of the target molecule. Alternatively, the capping group may be added after the last amino carboxylic acid unit has been coupled and deprotected.
The step by step synthesis is outlined in the following schemes. The second scheme is exemplary as the linker residue as well as the Cytxe2x80x2 residue may contain other functional groups as indicated in this scheme (see above): 
Accordingly, a further aspect of the invention is a process for the production of a compound of formula (I), characterised in that a compound of the general formula (V) 
wherein R1, Ra and Rb are as defined hereinabove, X1 represents OH, or a leaving group which is suitable to be substituted by a amino group,
is reacted with a compound HN(R4)xe2x80x94Cytxe2x80x2, wherein Cytxe2x80x2 is the residue of a cytotoxic or cytostatic compound, and R4 is as defined hereinabove.
Preferably, X1 within formula (V) is a leaving group, for example xe2x80x94Cl, xe2x80x94F, N-hydroxysuccinimidyl, pentafluorophenyl, or a carboxylate. Alternatively, X1 may be OH, and condensation is achieved by the use of an in situ coupling reagent, for example benzotriazole-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBOP), 1,1xe2x80x2-carbonyldimidazole (CDI), 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU), or 1-(mesitylene-2-sulfonyl)-3-nitro-1H-1,2,4-triazole (MSNT).
A further aspect of the invention is a process for the production of a compound of formula (I), characterised in that a compound of the general formula (VI) 
wherein R1, Ra and Rb are as defined in claim 1, Y1 represents Lxe2x80x94COX2, wherein L is a linker residue, and X2 represents OH, or a leaving group which is suitable to be substituted by a amino group or a hydroxy group,
is reacted with a compound H2Nxe2x80x94Cytxe2x80x2 or with a compound HOxe2x80x94Cytxe2x80x2, wherein Cytxe2x80x2 is the residue of a cytotoxic or cytostatic compound.
Preferably, X2 within formula (VI) is a leaving group, for example xe2x80x94Cl, xe2x80x94F, N-hydroxysuccinimidyl, pentafluorophenyl, or a carboxylate. Alternatively, X2 may be OH and condensation is achieved by the use of an in situ coupling reagent, for example benzotriazole-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBOP), 1,1xe2x80x2-carbonyldimidazole (CDI), 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU), or 1-(mesitylene-2-sulfonyl)-3-nitro-1H-1,2,4-triazole (MSNT).
A further aspect of the invention is a process for the production of a compound of formula (I), characterised in that a compound of the general formula (VII) 
wherein R1, Ra and Rb are as defined hereinabove, Y2 is of formula Lxe2x80x94OH or Lxe2x80x94NH2,
wherein L is a linker residue,
is reacted with a compound X3OCxe2x80x94Cytxe2x80x2, wherein X3 may be OH, or a leaving group which is suitable-to be substituted by a amino group or a hydroxy group, and wherein Cytxe2x80x2 is the residue of a-cytotoxic or cytostatic compound.
Preferably, X3 of the compound X3OCxe2x80x94Cytxe2x80x2 is a leaving group, for example xe2x80x94Cl, xe2x80x94F, N-hydroxysuccinimidyl, pentafluorophenyl, or a carboxylate. Alternatively, X may be OH and condensation is achieved by the use of an in situ coupling reagent, for example benzotriazole-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBOP), 1,1xe2x80x2-carbonyldimidazole (CDI), 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU), or 1-(mesitylene-2-sulfonyl)-3-nitro-1H-1,2,4-triazole (MSNT).
A further aspect of the invention is a process for the production of a compound of formula (I), characterised in that a compound H2Nxe2x80x94Cytxe2x80x2 is condensed stepwise with the units making up the compound of formula (I). Before each coupling step, it may be necessary to remove a protecting group PG, if present.
Accordingly, a further aspect of the invention is a process for the production of a compound of formula (I), characterised in that a compound of the general formula (VIII) 
wherein PG1 is a protecting group, and the other the substituents have the meaning as described before,
is reacted with a compound HN(R4)xe2x80x94Cytxe2x80x2, wherein Cytxe2x80x2 is the residue of a cytotoxic or cytostatic compound;
the protecting group PG1 is then removed and the resulting compound of formula (VIIIA) 
is subsequently reacted with a compound PG2xe2x80x94Axe2x80x94X4, wherein
PG2 is a protecting group, and X4 represents OH, or a leaving group suitable to be substituted by a amino group;
and further coupling steps are carried out, if necessary, until the complete compound is obtained.
PG1 and pG2 may be, for example BOC, or preferably FMOC.
Accordingly, a further aspect of the invention is a process for the production of a compound of formula (I), characterised in that a compound of formula PG3xe2x80x94N(R4)xe2x80x94Lxe2x80x94COX3, wherein
PG3 is a protecting group, and the other substituents have the meaning as described before, is reacted with a compound of formula Y4xe2x80x94Cytxe2x80x2, wherein
Cytxe2x80x2 is the residue of a cytotoxic or cytostatic compound; and Y4 represents H2N or HO; the protecting group PG3 is then removed; and the resulting compound HN(R4)xe2x80x94Lxe2x80x94Y4xe2x80x94Cytxe2x80x2 is reacted with a compound of formula (VIII) 
the protecting group PG1 is then removed and the resulting compound of formula 
is then reacted with a compound PG4xe2x80x94Axe2x80x94X4, wherein
xe2x80x83PG4 is a protection group, and X4 may be OH, or a leaving group suitable to be substituted by a amino group;
xe2x80x83and further coupling steps are carried out, if necessary, until the complete molecule is obtained.
A further aspect of the invention is a process for the production of a compound of formula (I), characterised in that
a compound of formula PG5xe2x80x94N(R4)xe2x80x94Lxe2x80x94Y5, wherein
PG5 represents a protecting group, Y5 represents OH or NH2 and the substituents have the meaning as described before,
is reacted with a compound of formula X5OCxe2x80x94Cytxe2x80x2, wherein
Cytxe2x80x2 is the residue of a cytotoxic or cytostatic compound and X5 is OH or a suitable leaving group;
the protecting group PG5 is then removed; and the resulting compound HN(R4)xe2x80x94Lxe2x80x94Y5xe2x80x94COxe2x80x94Cytxe2x80x2 is reacted with a compound of formula (VIII) 
the protecting group is then removed and the resulting compound 
is then reacted with a compound PG2xe2x80x94Axe2x80x94X4, wherein
xe2x80x83PG2 is a protecting group, and X4 represents OH, or a leaving group suitable to be substituted by a amino group;
and further coupling steps are carried out, if necessary, until complete molecule is obtained.
Another aspect of the present invention are the novel intermediate compounds of formula VIIIA 
wherein Ra, Rb, R4 and Cytxe2x80x2 are as defined hereinabove.
The compounds of the invention are intended for medical use. In particular, these compounds are useful for the treatment of tumours which are associated with stromal fibroblasts that express FAPxcex1 and which are generally not optimally treated with available cytotoxic and/or cytostatic agents. Tumours with this property are, for example, epithelial cancers, such as lung, breast, and colon carcinomas. Tumours, such as bone and soft tissue sarcomas which express FAPxcex1, may also be treated with these compounds.
Consequently, another aspect of the present invention are pharmaceutical compositions comprising a compound of the present invention and optionally one or more suitable and pharmaceutically acceptable excipients, as exemplified in: Remington: the science and practice of pharmacy. 19th ed. Easton: Mack Publ., 1995. The pharmaceutical compositions may be formulated as solids or solutions. Solid formulations may be for preparation of a solution before injection. Preferably, the pharmaceutical compositions of the invention are solutions for injection. They may be administered systemically, e.g. by intravenous injection, or topically, e.g. by direct injection into the tumour site. The dosage will be adjusted according to factors like body weight and health status of the patient, nature of the underlying disease, therapeutic window of the compound to be applied, solubility, and the like. It is within the knowledge of the expert to adjust dosage appropriately. For doxorubicin conjugates, for example, the dose will preferably be in the range from 10 mg/m2 to 1350 mg/m2, but also higher or lower doses may be appropriate.
Accordingly, a further aspect of the present invention is the use of a compound of the invention in the preparation of a pharmaceutical composition for the treatment of cancer. Furthermore, an aspect of the invention is a method of treatment of cancer, comprising administering an effective amount of a pharmaceutical composition of the invention to a patient. Indications include the treatment of cancer, specifically,
1) The treatment of epithelial carcinomas including breast, lung, colorectal, head and neck, pancreatic, ovarian, bladder, gastric, skin, endometrial, ovarian, testicular, esophageal, prostatic and renal origin;
2) Bone and soft-tissue sarcomas: Osteosarcoma, chondrosarcoma, fibrosarcoma, malignant fibrous histiocytoma (MFH), leiomyosarcoma;
3) Hematopoietic malignancies: Hodgkin""s and non-Hodgkin""s lymphomas;
4) Neuroectodermal tumors: Peripheral nerve tumors, astrocytomas, melanomas;
5) Mesotheliomas.
Also included are the treatment of chronic inflammatory conditions such as rheumatoid arthritis, osteoarthritis, liver cirrhosis, lung fibrosis, arteriosclerosis, and abnormal wound healing.
A further aspect of the invention is a method of treatment of cancer, wherein a prodrug is administered to a patient wherein said prodrug is capable of being converted into a cytotoxic or cytostatic drug by an enzymatic activity, said enzymatic activity being the expression product of cells associated with tunour tissue. Preferably, said enzymatic activity is the proteolytic activity of FAPxcex1.
One method of administration of the compounds is intravenous infusion. Other possible routes of administration include intraperitoneal (either as a bolus or infusion), intramuscular or intratumoral injection. Where appropriate, direct application may also be possible (for example, lung fibrosis).